Mind Gazer

Dash {2}{u}{b} (You may cast this spell for its dash cost. If
you do, it gains haste, and it's returned from the battlefield to
its owner's hand at the beginning of the next end step.)
Whenever Mind Gazer enters the battlefield, purge the top card of
target player's library. (To purge a card, put it into
it's owner's graveyard.)